You might try to install an event filter on the scroll bars of the QScrollArea, and listen for the showEvent. If it is not spontaneous, it came from the application itself. I think that would equate to the QScrollArea showing the widget. There are no signals you can use that I am aware of.

Thanks for the advices.

I really thought Qt would manage the appearance of the scrollbar with signals.
I’ll try the eventfilter based in the showEvent.